联盟 (古罗马)（拉丁语：foederati），在古罗马时代而言，是专指最初罗马共和国的部落结盟，该结盟直至罗马帝国晚期，甚至以不同方式还存在着。罗马共和国初期，罗马条约订定，促进了这次联盟，联盟联系着古罗马不同部落与其殖民地，并以联盟公权力，来解决着部落间任何问题。古罗马维持一定数量的联盟，其中以拉齐奥最具代表性。

Foederatus (/ˌfɛdəˈreɪtəs/ in English; pl. foederati /ˌfɛdəˈreɪtaɪ/) was any one of several outlying nations to which ancient Rome provided benefits in exchange for military assistance. The term was also used, especially under the Roman Empire for groups of "barbarian" mercenaries of various sizes, who were typically allowed to settle within the Empire.